ALFA ROMEO 159

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ROADHOLDING: AN ENTERTAINING DRIVE AND ACTIVE SAFETY
 

The new Alfa 159 states that it is an Alfa through and through, by guaranteeing control and entertaining driving that admit no compromise. Travelling comfort and dynamic behaviour have always been hallmarks of Alfa Romeo cars, and they become real strengths on this model. To start with, the Alfa 159 has a very interesting suspension layout, the fruit of a new project that set extremely high standards of excellence: it has "high" double wishbones at the front, and a multilink system at the rear. This means a greater capacity to absorb road roughness, more linearity and precision in response to the steering (the most direct of the standard saloons, with a small turning circle), superb roadholding, maximum stability in high speed manoeuvres and the agility of a true Alfa Romeo on narrow mixed routes. The solutions adopted and the advantages that will be perceived immediately by the motorist are described in detail below.

Front suspension and steering

The new high wishbone layout adopted on the front suspension is the ideal solution to guarantee precise control of wheel movement, with a clearly defined steering axis. The architecture was borrowed from racing and endows the car with outstanding dynamic performance, and extremely sensitive, pinpoint steering. The high double wishbone was already used on the 156 and has been further improved on the new Alfa 159.

First of all, the steering axis was brought closer to the centre of the wheel, increasing the Ackerman level (to increase parallel wheel movement when steering) for better response when cornering, thanks to the steering which is the most direct in its category. The steering of the new Alfa 159 has an excellent ratio (12.7 steer for every degree of wheel steer) which translates into a more direct response for the driver, more responsive steering and better stability control. What is more, painstaking analysis of the matching of the steering geometry and the wheelarch volume, made it possible to achieve high steering angles even with the largest tyres, and this significantly improved the turning circle between kerbs (11.1 metres).

Great attention was paid to the new wheel upright where it connects to the levers, exploiting the available space inside the rims in full, and this has significant advantages in terms of lateral rigidity; the size of the coaxial damper spring unit has been increased to improve its capacity to absorb road roughness; the aluminium lower wishbone combines excellent structural characteristics and a much lower weight; the upper aluminium arm fits a pair of dry friction sliding bushes, a solution chosen because it is stronger and more reliable, and guarantees a more progressive action. And finally, the suspension is connected to the chassis by a closed geometry frame which is stiffer than the previous solution which had a simple crossbeam.

Rear suspension

The new Multilink rear suspension allows wheel movement to be controlled in a sophisticated manner, reaching the best possible balance in terms of performance. The system with three levers and a transverse blade highlights the performance of the various components subject to a longitudinal load, to improve the filtering of roughness and under a lateral load, achieving faster responses, enhanced stability and extreme grip.

The rear suspension of the Alfa 159 now features:

  • A higher anchorage point of the longitudinal link, which is now positioned higher than the centre of the wheel, allowing the suspension to perform a longer, more flexible stroke, with an optimal response when negotiating an obstacle.

  • The aluminium upright, fitted with a third generation, extremely rigid hub, supports the connection bushes for the camber lever and the longitudinal link.

  • The bi-tube spring-damper unit is larger than other conventional solutions, this achieves a better compromise between handling and comfort.

  • The camber link, which allows the static camber to be adjusted and produces a geometry capable of guaranteeing a good camber recovery with wheel shake to ensure that the wheel rests perfectly on the road and wear is thus uniform, even when the car is pushed to the limit.

  • The rear hydraulic bush guarantees excellent filtering of roughness, and allows the wheel to retract slightly when negotiating an obstacle.

  • A high yield steel crossbeam isolated from the bodyshell by four elastic bushes that dampen high frequency vibration.

The Alfa Romeo Q4 four-wheel drive system

The new Alfa 159 proposes an evolution of the permanent 4x4 system with three differentials (with a Torsen C self-locking unit at the centre) already adopted on the Crosswagon Q4. The heart of this project is the "Alfa Romeo Q4 four-wheel drive" system which splits torque constantly and dynamically between the four wheels, reaching the highest levels of active safety and sportiness. The Torsen C self-locking differential sends drive torque 57% to the rear wheels and 43% to the front. The system also guarantees excellent traction in all grip conditions by automatically checking slip.

The torque split between the front and rear axles is modulated constantly by the Torsen C central differential on the basis of grip. This feature harnesses sportiness to enhance active safety. Modulation is mechanical, continuous and gradual, to enhance the perception of optimal, enjoyable, easy driving. There are no gaps in the torque delivery. Where grip is concerned, the behaviour adapts gradually and smoothly to changing road conditions. This "mechanical" control is backed up by electronic stability control, which boosts performance and safety margins, in line with the Alfa Romeo philosophy. The four-wheel drive car is the state of the art in technical terms and offers important advantages.
 

Alfa Romeo 159
Alfa Romeo 159
Alfa Romeo 159
Alfa Romeo 159
Alfa Romeo 159
Alfa Romeo 159

 

  • Q4 permanent four-wheel drive with a Torsen C self-locking differential makes for better roadholding, entertainment and smooth responses. Other technological archetypes with electronically controlled joints do not achieve the optimal balance between understeer and oversteer or the smoothness that are innate in the Alfa 159, and translate into superb active safety.
     

  • The torque split in favour of the rear axle makes driving even more entertaining, because it makes the car even easier to handle, without detracting in any way from stability during sudden lane changes on the motorway, or other emergency manoeuvres.
     

  • The ability to travel safely in poor grip conditions without the aid of electronics in torque split for constant driving pleasure.

We could say that the Alfa 159 Q4 interprets four-wheel drive from the Alfa Romeo point of view: it is basically a "mechanical" system enhanced by cutting edge electronic technology to guarantee maximum comfort and entertainment, combined with superb performance and absolute safety.

Sophisticated technology for total control

The Alfa 159 adopts the most sophisticated electronic systems to control the car's dynamic behaviour, and to raise the dynamic limits even higher, so that they increase safety but are not intrusive for the driver. The intervention of these devices was studied in simulations and exhausting track tests to ensure that the car is always entertaining to drive. The Alfa 159's lavish array of safety equipment is described below.

ABS complete with EBD

The Alfa 159 features an excellent braking system backed up by the BOSCH 5.7 ABS anti-lock braking device, one of the most advanced on the market. It has four active sensors and a hydraulic control unit with 12 solenoids. The ABS system incorporates Electronic Brake force Distribution (EBD), which distributes the braking effort to the four wheels so that it prevents them from locking, maintaining full control of the car in all conditions. The system also adapts to the grip conditions of the wheels themselves and the efficiency of the brake pads, thus preventing the latter from overheating.

VDC (Vehicle Dynamic Control)

VDC is Alfa Romeo's interpretation of ESP (Electronic Stability Program), the system that intervenes when conditions are close to the limit and the car's stability is at risk, to help the driver to control the car. VDC is a sporty device, as you would expect of an Alfa, with excellent roadholding, and lets the driver enjoy total control of the vehicle as long as conditions are normal, only intervening just before the situation becomes critical. The VDC system is always engaged.

On the other hand, MSR (Motor Schleppmoment Regelung) intervenes if he changes down suddenly in poor grip conditions, giving torque back to the engine to prevent skidding due to wheel lock. To do this, VDC constantly monitors tyre grip on the road, both longitudinally and laterally, and if it detects a tendency to skid, the system intervenes to recover direction and stability. Sensors measure the rotation of the car around its vertical axis (yaw speed), the lateral acceleration and the steering lock set by the driver (which indicates his chosen direction). It compares these data with the parameters elaborated by an electronic control unit and uses a complex mathematical model to establish whether the car is taking a corner within the grip limits, or if it is about to skid at the front or the rear (understeer or oversteer).

To recover the correct trajectory, the system generates a yaw contrary to the one that is causing the instability, braking the relevant wheel (inside or outside) individually and reducing the engine power (by adjusting the throttle valve). This is the peculiar feature of the device developed by the Alfa Romeo engineers. The brake adjustments are modulated so that they are as smooth as possible (and will not disturb the driver) and the reduction in engine power is also limited, to guarantee excellent performance at all times and superbly enjoyable driving.

VDC performs this complex task by communicating constantly not only with the brake sensors and the engine control unit, but also with:

  • the "Body computer" which constantly exchanges information with the ABS system, and the control units of the engine and automatic transmission;

  • the electronic throttle valve (which in turn dialogues with the ABS system);

  • the instrument panel (active telltales);

  • the steering wheel and steering column (via the steering sensor);

  • the gyroscopic sensor installed on the cabin floor to record yaw and lateral acceleration.

    ASR (Anti Slip Regulation)

    ASR (Anti Slip Regulation) is an integral part of the VDC system, optimising traction at all speeds, assisted by the brakes and the engine control. The device monitors the wheel speed calculated by the ABS sensors to establish the amount of slip and triggers two different control systems to recover grip. When an excessive demand for power causes both drive wheels to slip (for example, aquaplaning or accelerating on an uneven, snow-covered or icy road surface), the system reduces engine torque by decreasing the throttle valve aperture and thus the air flow.

    If, on the other hand, only one wheel slips (for example the wheel on the inside of the bend, after acceleration or a dynamic change in the load), this wheel is automatically braked without the driver having to touch the bake pedal. The effect is similar to that of a self-locking differential. This gets the Alfa 159 out of any difficulties on surfaces where grip is poor. ASR is engaged automatically every time the engine is started, but can be excluded by a pushbutton on the central console. ASR must be excluded when snow chains are fitted because in this case, in order to transmit torque to the ground, the wheel needs to be able to "accumulate" the snow, with small slips that the ASR tends to avoid.

    HBA and Hill-holder

    The safety equipment on the Alfa 159 is completed by the HBA system, the hydraulic electronic hydraulic braking assistant which automatically increases the pressure in the braking circuit during emergency braking. And by the Hill-holder system, which maintains the braking pressure for a few moments after the driver removes his foot from the pedal, to simplify hill starts and prevent the car from slipping backwards.

  • Text & Photos: Alfa Romeo